The present invention relates to a variable displacement swash-plate compressor.
Japanese Laid-Open Patent Publication No. 52-131204 discloses a conventional variable displacement swash-plate compressor (hereinafter, referred to as a compressor). The compressor includes a swash plate chamber, cylinder bores, a suction chamber, and a discharge chamber, which are provided in the housing. The housing rotationally supports a drive shaft with the distal end of the drive shaft projecting out of the housing. The swash plate chamber accommodates a swash plate, which is rotational through rotation of the drive shaft. A link mechanism is located between the drive shaft and the swash plate. The link mechanism allows the inclination angle of the swash plate to be changed. The inclination angle is the angle of the swash plate in relation to a direction perpendicular to the axis of the drive shaft. Each cylinder bore reciprocally accommodates a piston. A conversion mechanism reciprocates each of the pistons in the associated one of the cylinder bores by the stroke corresponding to the inclination angle through rotation of the swash plate. The inclination angle of the swash plate is changed by an actuator. The actuator is controlled by a control mechanism. The control mechanism includes a pressure regulation valve.
The link mechanism includes a lug member, a hinge ball, and a link. The lug member is located in the swash plate chamber and is fixed to the drive shaft. The hinge ball is fitted about the drive shaft to be arranged between the swash plate and the drive shaft. The hinge ball includes a spherical portion, which slidably contacts the swash plate, and a receiving portion, which faces the actuator. The link is provided between the lug member and the swash plate. The link connects the swash plate to the lug member, so that the swash plate is permitted to pivot.
The actuator includes the lug member, a movable body, and a control pressure chamber. The movable body has a cylindrical shape that is coaxial with the drive shaft axis. The movable body is fitted about the drive shaft to be arranged between the lug member and the hinge ball. The movable body changes the inclination angle of the swash plate by moving along the axis of the drive shaft. The movable body includes a large diameter portion and a small diameter portion, which extends from the large diameter portion toward the hinge ball. The side of the small diameter portion that faces the hinge ball serves as an acting surface, which contacts the receiving portion at an acting position. When the acting portion and the receiving contact each other, the movable body is engaged with the swash plate via the hinge ball. The control pressure chamber, which is defined by the lug member and the movable body, uses its internal pressure to move the movable body.
In this compressor, when the control mechanism connects the discharge chamber and the control pressure chamber with each other using the pressure regulation valve, the pressure in the control pressure chamber is increased. This moves the movable body along the axis of the drive shaft and causes the acting portion to press the receiving portion along the axis of the drive shaft. Accordingly, the hinge ball is moved along the axis of the drive shaft, and the swash plate slides on the hinge ball in the direction reducing the inclination angle. This allows the displacement of the compressor per rotation of the drive shaft to be reduced.
However, in the above described conventional compressor, the stroke of the movable body required for changing the inclination angle is large, which results in an increased axial length of the compressor. This restricts the size reduction of the compressor.